1. Field of the Invention
This invention relates to a direct drive motor, particularly for use in the capstan spindle of a tape player.
2. Description of the Prior Art
Recently there has been a tendency of tape players and VTRs toward miniaturization and lightening. The application of a direct drive motor to a capstan spindle has been used for this purpose.
FIG. 7 is an elevational view of an example of such a prior art direct drive motor driving a capstan spindle of a tape player for feeding a tape. The capstan spindle is held at the upper and lower end portions by bearings 2,2. The bearings 2,2 are force-fitted in an upright housing 4 mounted on a base 3. To the bottom 1a of the capstan spindle 1, a rotor 5 is secured through a boss 6. The rotor carries a set of magnets 7, 7. the above-mentioned base 3 is provided on the underside with a yoke 9 and a set of coils 8, 8 opposite to the magnets 7, 7.
The capstan spindle 1 abuts at its upper end 1b against a thrust plate 11 made of a low friction material. The thrust plate 11 is fitted in the bottom with a screw 10 screwed in the upper end of the housing 4. The upward (in the drawing) force applied to the capstan spindle 1 resulting from the magnetic force of attraction between the magnet 7 and the coil 8 is countered by the abutment of the upper end (1b) of the capstan spindle 1 against the thrust plate 11 in the thrust direction. The mechanism enables adjustment of the gap between the magnets 7 and coils 8 by turning the screw 10 accompanied by the vertical displacement of the thrust plate 11.
The capstan spindle 1 is exposed through an opening 4a formed on one side of the housing 4. The exposed portion is opposite to a pinch roller to be abutted against it. The prior art direct drive motor mentioned above has the following defects or disadvantages:
(1) The capstan spindle 1 is, at the upper end 1b, held in the radial direction by the bearing 2 and in the thrust direction by the thrust plate 11. This design requires a number of parts for holding the upper end 1b of the capstan spindle, which complicates the assembly and adds a correspondingly-higher cost. The separate attachment of the screw 10 and the upper bearing 2 contributes to the added height of the product which hinders miniaturization.
(2) The bearings 2, 2 are forced-fitted in the upper and lower end portions of the housing 4 respectively, so as not to allow radial movement. This requires highly precise assembly to ensure the accurate setting of which is more complicated hence, involving complicated work.